So, I gave Byzantium a shot, fully expecting to be wiped off the map by a vengeful Ottoman Empire with seven times my troop count. Instead I've bungled into getting a bunch of land back from Venice and the various minors (though Crimea forced me to concede Kaffa). I'm still nowhere strong enough to take on the big green with something like 18K troops vs their 42K.

But a weird thing happened. When I retook a province, it gave me a +15 or so modifier to each of my administration score when determining my world ranking, propelling me to #1 in the world by a long shot and allowing me to build up enough score to become the #7 world power before vanishing. All conquests since (and all conquests by NPCs) give +0.0. What the hell happened here?